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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3eac5976e70937860e23a9fb8b69702a4820aefa55ecb57d037084bf363c9c2' 
  AND token = 'U3UHMutRc6QtJ7TlhL1UvyS5Ar6nH8dIn8x4e8kUP5c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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