SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42351055f6e0a3f03e3ee756123ce7238bab3ca2add1af50aa6d7d68a076ccbe' 
  AND token = 'zfE+p72PhcIjZ66Glsa0AYDLpL8hNAxbed2ZoVEXwzQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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