SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3a399a392c85777a7cc9138693c30de390b664e48009213b251af603d29bcd6' 
  AND token = 'iLVUdhdJMyhItghtilSB5wEQEvO4NoGM6OF9MgJb4VQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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