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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c1a8e27f3b3db8d1395abc7c764bea4eee65df05f7cc5ff2ecea14df01731d' 
  AND token = 'oLSQWBsLoqxnktM8wUJiTDh+x7hltJO7I0vDt0Naalc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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