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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '77f5a8818c8ec0db94932e43acc91b0a4cb2b2300e0bb15c18f1a88b4cf0e891' 
  AND token = 'py8i5jWkArk7D2aKSgtNWRRIB4gkMtQAagMi12g0bbk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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