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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4e0c6651c4549629061f5c9890a1d7e42a6c100edcf11b2c8e4cc757f75bb6d' 
  AND token = 'gT/ijolNwLYZig88a6Qm4rc3eV9kUgLQYnVjSSOJ1Qw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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