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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e6fd5cb78ea6ba34d6b1ab59df2bc7fef97194fcc78c8516d58fc19e2d0855' 
  AND token = 'V4yy+sHUSOr1IDMARzb7hERZwk/+99idQojlyaW2tCY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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