SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '51d5b400d939a880a2cddc9c2f0a6feaccfea34342b960a94a5950c2fc844d22' 
  AND token = 'BnAA2+5Zz0OxjbIHRGXRXnZ5hjgOswn91b/TcQLoqVs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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