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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f1e97e374db048ed0f419efda2eba4cf59394fd53fa7a8f7187329bc8e2c575' 
  AND token = '0sPcIgmXnNmQQMAmyoTCmLXmeud6euJTM9RgVZ+65Pc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}