SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76f92777abb7abf0d280e9e333bd8079eb83d3de913089eaef19647a37245443' 
  AND token = 'r0Ky1F8/lCSpLftKV4GTtTK3sr/GEMxO3eqcm+9aJR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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