SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b2c51c02b6159fb822e2b293e6ff6550735d3532ed523c854e1c1b626f8eb31' 
  AND token = 'c2FBAs9zMSMGNfd7z3XmNF/QwwdMfdUqCsSmBKiERmI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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