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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df4a1667698fc62f25d2570d27865b9f352b58a21f50e2e212ddf5750c31fa6a' 
  AND token = 'uOuf+fu2lmf2gEVJhezm8MStWMMukdFKJVrD/gagERs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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