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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df3fdf5c62896c0485689ea3a91228c1c8fbf052f63311b77108639793937122' 
  AND token = 'kslTGaopSmXxjBb4sZlXZPTjRgtvrKyTvFXXc2829nM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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