SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cc959f886748ff995041487b71e048342dd6548ca16d478883aac2efe95f2578' 
  AND token = 'k1rHtsNhuEEckThgSx3R7gRniMsOqH8MjF+rnl69UzE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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