SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '912760c3ee35634b6231498de68d309c89b196af36e4a7f2a95b6c73c4113381' 
  AND token = 'jWy0Iew1+hl+VwPybYgYsvIp1OpLHefmmBSUjGGeUQE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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