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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b642c6dbdaa00328442a95e2dcf0f0c4ac8089eb2d9599bcd7741f24d26ce0c4' 
  AND token = 'sOoa37RYkbHRNABaeXevW+3hTc+4RIkqZDJETRvLOz8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}