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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3210c4d3cd2f010fded983ea03dcc630ea7f30c80e268c1d02d2e34a327cac9' 
  AND token = 'DDf+jCXtKtozoQLxTdS9PkV2nqWUoLs1GvzWbK/qeyM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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