SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71b85ec1797888eb40c1c2820e418f90ea0701f2975da2504434837deee98a93' 
  AND token = '7NxX8RnrywegtXZGzSKaThb+qyLeHbWO8lvl4ws8K0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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