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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '785f3aed1067e3e0fdb19c1917319bff5ff7bd729b950153c3ddef5643d5b37c' 
  AND token = 'bj+fSux9mMrECSzcavZaUAe3JSIz2yx4+UXcQFurMtg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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