SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e56b0132755edcf745e286d5a5728cfd5362ddf646132993e51d186d8120d2e5' 
  AND token = 'uznmxFOsDAJREjelgDsIVNIvXrDuqhzuGBaBi/Gnzyw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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