SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac3eb3c2370e8768d11da57bb5f1635e0841811e3631ac2556ec334f0ec64c0a' 
  AND token = 'QHWtGNikHp2bjQTK45EQhxAIAClJyg0q4p2EFw889vQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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