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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3c177cb4843f3ae0b62df1f59e29e67a4fa2fd5643aa8a397c44f27291f1caa' 
  AND token = 'PxpftKoOiI4WtlweIFylR2FhRf6ZbTcFdLQOSr6LZ+w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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