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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9c520e5a4684e0cf3397d121e24ce6d8bc1c55d20a63cb5d05a8b2879d04e3c' 
  AND token = 'muaE3K2t8roQ+on/kk0p0CjWYKhGDeBstOIZSHENoXQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00010

JSON explain

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