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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8b8af0b9e0bf2db031c4a43e54f76881e52c6476499b8c7f52d08e9c9583ed0' 
  AND token = 'hDfI/yyto+OGqE/uyGbEigLrhQqwbOEMsbbyRiS8Vq8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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