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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6ddfda90e8052ca566eadca02cf44df1b9acf80196ed499e6e503979fdf0777' 
  AND token = 'pQLqHjE0D3SsgRqeDPsAfa5atFteTcUmfCTbt+I1n2w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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