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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e3b5cd5be2a5d20cff1e490ac925ef45eb78d4406fb4ac69d0ba2b8d20f6a436' 
  AND token = 'vRXPtoxnsY7JTt2eDqC7FYqsTea/J1sNfJIEup/8H90=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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