SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51c492788e6f6f4f7291328402dfd083ff33c400615d5653e5bea95557e39bc0' 
  AND token = 'EEsVGKAoKV0Td2UHArBU9sd6bmNMu7ItXOauCIftfYE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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